Auscultation microphone



A. 35, 21939 c LIAN ET ALL AUSCULTATION MICROPHONE Filed April 27, 19 37 ll ///////x A INVENTORS CAMILLE LLaAN Qaomss MINO a Arm/aways Patented Aug. 15, 1939 UNITED s'rAr s PATENT orrice AUSCULTATION MICROPHONE Camille Lian, Paris, and Georges Minot, Ezanville, France Application April 27, 1937, Serial No. 139,318

' In France May 5,1936

4 Claims.

The present invention relates to auscultation microphones, i. e. to electrical apparatus able to transform into electric oscillations the sonorous vibrations of the thoracic wall of a living being, and in a quite accurate manner so as the frequencies exactly coincide with those of the s norous vibrations and that amplitudes are at any moment proportional.

In auscultation microphones heretofore used, a

rod having a pad on one end is in contact withthe region to be explored and the other end of the rod bears an armature vibrating in front of an electrical field element, the arrangement of which is different according as the microphone is elec-' tro-magnetic, electro-static, electrodynamic, etc.

Hitherto this electrical field element was quite .stationary and fixed to the casing of the apparatus and this arrangement presented some drawbacks, as the armature was influenced by the movements of the explored region and particularly by the slow movements of cardiac or respiratory origin. Consequently, relative movements occurred between the armature and the electrical field element and changed the conditions of operation of the microphone, deforming the figurative curves, altering the sensibility of the microphone and sometimes producing parasitic oscillations resulting frolnnon-dampend shocks.

Besides, in most microphonesthe armatures were not protected and they collected oscillations resulting from external sounds, (for instance articular sounds of fingers of the operator or sounds emitted by the loud-speaking telephone which reproduces the oscillations). I

The present invention has for its .object' to obviate these drawbacks, rendering the microphone insensible relatively to infra-sonorous vibrations,

. having for instance a frequency lower than or 30 per second-and by protecting the -movable armature and the electric field element against parasitic acoustic-vibrations.

To this efiect, according to the invention, the electrical field-element of the microphone is supported by the movable armature itself through the intermediary of an elastic support which is dampened either by itself or .by a distinct darn-- 'The mass. of the electrical fieldelement and the.

elasticity of the support are determinedso that 7 this support remains stationary when the vibrations of the movable armature have a frequency higher than 'the chosen amount (20 or '30 per second)- The'dampening' of the support'is determined so that the whole (is aperiodic; in other words, if the field element is moved, it comes back to its-normal position without oscillations on both ,sides from this latter.

Owing to this arrangement, the infra-sonorous vibrations and motions are transmitted through the support towards the field element, so that the relative movements of both parts are, small. The sensitivity of microphone and its accuracy are not altered, for it operates in the same may be used'near a loud-speaking telephone reproducing the registered sounds, without untimely entertained oscillations.

The invention is illustrated by way of example in the annexed drawing in which:

Fig. .1 shows diagrammatically the general arrangement of themicrophone.

Fig.2 is a section showing a preferred form of construction'of the microphone. I

On this drawing are seen some parts of an ordinary microphone, that is to say a pad Ill in contact with the region to be explored and connected by a rod II to a movable armature 12 lo- 1 cated in front of an electrical field element l3 capable of transforming into electrical oscillations the mechanical vibrations of the arma-' ture I 2, In conformity with the invention, the field element I3, having a suitable'mass, is borne'by the armature l2 itself-by yielding supporting constituted by elastic curved blades l4 between branches of which are cushions I5 of a dampening material 'such as felt, rubber and the like.

The rod ll isfconnected to the centre of an elastic cross l6 fixed at the ends of its branches to acasingl'l. v

The microphone operates as follows:

- Owing,to inertia of the field element l3 and a "periodicity due to cushions IS, the armature I2 is able to vibrate with sonorous frequencies without a substantial movement of the field element l3. On the contrary the slow andlow-frequency I motions imparted to the armature I2 are transmitted through the support 14 to' the .field element I3,' so that no relative movement takes place between the armature and the field element, and owing to this peculiarity, the sensitivity and accuracy of the microphone are not altered.

In the general arrangement of themicrophone in conformity with the invention shown on Fig. litisassumedthatthesupportingmeans l4 and ii between'the armature I! and the field element is are perfectly elastic and perfectly ring Il.-

dampened, respectively.

In practice-any material presents together elasticity and dampening, and the material will be chosen according to the purpose considered.

Thus according tothe form ot construction shown in'rig. 2, the microphone (of electromagnetic type) comprises an. electrical field element constituted by an electro-magnet i3 fixed to a relatively thick rubber sleeve 20, for instance by means of a suitable adhesive layer I 9; A plate 12 Iormingthe movable armature of the electromagneti3 is engaged by its ends in-the rubber The same microphone comprises also therod i I,

I thepad II and the elastic cross I. This latter details without and the electrical field element ll.

The metallic casing i1 is an electro-static screen and protects the microphone against external electric disturbances.

The rubber envelope 2! completes the casing as it protects the microphone against outer noise and particularly against sounds coming from fingers of the operator. i A

It is evi ent that the'invention is not limited to the example which is hereinbeiore described and that its construction may be'modified in its departing from the spirit oi. the invention.

For instance suitable modifications will be adopted according to whether the microphone is electro magnetic, or electro-static or electrodynamic. etc. j

In the same way, itis evident that the microphone in conformity with the invention could be tween the aioaeoo used not only for auscultation but'to collect sonorous vibrations in a solid body, exclusive of slow movements and of external vibrations.

We claim:

1. An auscultation microphone comprising; in

combination, a casing, a rod projecting outward ly from the swing and carrying'at-its exterior extremity an element adapted to make contact lati'ons, yielding supporting means for securing I Y said rod on said casing, and other yielding supporting means for securing the field element on the armature.

2. An auscultation microphone in accordance with claim 1, comprising cushioning means hearmature and, the electric field element.

-3. An auscultation microphone comprising, in combination, a casing, a rod projecting outward 1y irom the casing and carrying at its exterior extremity an element adapted to make contact with the part'to be auscultated, a movable armature attached to the inner extremity of said rod in the interior of the casing, an electric field element adjacent said armature adapted to transform the armature vibrations into electric oscillations, and yielding supporting means for the electric field element secured on said armature, said means comprising elastic blades fixed on the armature and the electric field element, a cushion member being inserted between the armature and the electric field element.

4. An auscultation microphone comprising, in

combination, a casing, a rod projecting outwardly irom the casing and carrying at-its exterior extremity an element adapted to make contact with the part to be auscultated, a movable armature and supporting the electric field element.

CAMILLE LIAN. GEORGES mar.

armature and lo 

